Not Applicable
Not Applicable
This invention relates generally to electrical interconnection devices, and more particularly to resilient electrical interconnection devices.
Resilient interconnects that provide electrical connection between opposing planar surfaces are known, and generally comprise an elastomeric or polymeric material containing conductive particles disposed in the material to provide a conductive path between a first surface and a second surface. In one version the interconnects are shaped as elongated columns providing a conductive path between the end faces or surfaces thereof, as shown in co-pending application Ser. No. 08/736,830, filed Oct. 28, 1996 now U.S. Pat. No. 5,949,029, issued Sep. 7, 1999.
Such resilient interconnects can be used to provide electrical connection between a printed circuit board and an integrated circuit or other device. For such a use, the resilient interconnects are disposed in respective openings in a substrate which are arranged in a predetermined pattern. Such a substrate can be a circuit board itself or a separate substrate attachable to a circuit board. The integrated circuit or other device has an array of contacts that correspond to the pattern of resilient interconnects disposed in the substrate. The integrated circuit or other device is mounted in the substrate by aligning the contacts with the resilient interconnects, applying force against the integrated circuit or device so that the resilient interconnects are compressed against the contacts, and then securing the integrated circuit or device to maintain intended contact force.
Complications may occur when a relatively large array of resilient interconnects is employed. Because each resilient interconnect must be deflected to a sufficient degree to establish and maintain electrical connection, the amount of force required to seat the integrated circuit or other device on the printed circuit board increases in proportion to the number of resilient interconnects that are employed. The amount of force that is required may hinder assembly. Further, as the number of interconnects employed is increased, there is an increased risk that satisfactory connection will not be established with all the interconnects, especially where a mating circuit board surface is warped or irregular. In some instances, the resistant interconnects will not be sufficiently compressed to make electrical contact or proper electrical contact, while in other instances the resilient interconnects may be excessively compressed such that misalignment can occur. The misalignment of a resilient interconnect and a mating contact can result in improper engagement of the interconnect with an adjacent contact or short circuiting of one or more contacts.
In accordance with the present invention, resilient electrical interconnects are provided which have a non-uniform cross section which achieves an increased range of deflection and a predetermined relationship between compression force and deflection of the interconnect, and between resistance as a function of deflection. A smaller cross sectional area decreases the spring rate, or compression force, of the interconnect during compression. Increased range of deflection and reduced spring rate enables improved compensation for surface irregularities and facilitates mounting of integrated circuit or other devices having large arrays of interconnects. The non-uniform cross section is provided by a single or compound slope, or alternatively a nonlinear curve, from the end of smaller cross-section to the end of larger cross-section.
Various embodiments as disclosed herein encompass shapes of tapered columns having a straight line contour along the entire height, a contour following a plurality of straight lines at different angles, and a contour following a curve. Conductive material used to make the interconnect, such as a polymeric material with conductive particles, provide the necessary conductivity between the opposed ends of the interconnect. The end of the interconnect having the larger cross-section provides a base for mounting on a fixed contact surface, such as a circuit board or socket, while the end having the smaller cross section provides a contact end for contacting a conductive pad or terminal on the mating device. The broader base stabilizes the interconnect and maintains alignment of the contact end to minimize lateral movement of the interconnect to avoid adjacent interconnects from contacting each other or from contacting an incorrect conductive pad on the mating device.